Mouthparts

Mouthparts of honey bee worker (posterior view). After Michener (1974, fig. 1.6) [1]. The mouthparts are unfolded and spread apart. Most of the time they are folded behind the head and held together. See also mechanism of folding of the mouthparts.
Cd - cardo (plural cardines)
Ga - galea
Gls - glossa (tongue)
Lbl - labellum
LbPlp - labial palpus
Lr - lorum [2], submentum [1]
MxPlp - maxillary palpus
Pgl - paraglossa
Pmt - postmentum [2], mentum [1]
Prmt - prementum
St - stipes
The glossa is similar to a long cylinder. The diameter of the glossa is 185.0±1.5 micrometers at the base and 96.6±0.3 micrometers in the middle part. The glossa consists of segments. Length of one segment is about 23 micrometers. On apical part of each of the segments there are 16-20 hairs. The hairs on basal part of the glossa are stiff and short (32 - 63 micrometers long), whereas the hairs on the middle and apical part are longer (171.9±0.3 micrometers long) [3]. At the apex of the glossa there is a spoon-like flabellum. The mouthparts are cleaned with foreleg tarsi [4].
Ingesting liquid food by bees is based on mechanism of "viscous dipping" [5]. The tongue is extended and immersed into nectar. At this stage hairs on the glossa erect asynchronously [6][7] and trap the nectar [8], see also video [5]. The erectable hairs can increase the ability of a bee to collect nectar [3]. Next, when coated with nectar, the glossa is retracted to a tube formed from galeae and labial palpi. Then the nectar is sucked into pharynx. There are ridges on the inner wall of galeae which can reduce friction during drinking [9][10]. Honey bees are able to imbibe 1.8 microlitres of diluted nectar per second [11]. This rate is lower in case of higher concentrations of nectar [11]. It was suggested that the optimal for bees concentration of sugar in nectar, which is a compromise between energy content and intake speed is about 52% [5] but see [3]. There are sensory organs on the mouthparts which facilitate the food intake [12][13][14][15].
References
- The social behavior of the bees: a comparative study. Harvard Univ. Press., Cambridge, Mass. (1974)
- Anatomy of the honey bee. Comstock Publishing Associates, Ithaca, pp. 334. (1956)
- Effects of erectable glossal hairs on a honeybee's nectar-drinking strategy. Applied Physics Letters 104:263701. (2014)
- Mouthpart grooming behavior in honeybees: kinematics and sectionalized friction between foreleg tarsi and proboscises. Journal of insect physiology. (2015)
- Optimal concentrations in nectar feeding. Proc. Natl Acad. Sci. USA 108:16618-16621. (2011)
- Erection pattern and section-wise wettability of a honeybee's glossal hairs in nectar feeding. Journal of experimental biology (in press). (2015)
- Erection mechanism of glossal hairs during honeybee feeding. Journal of Theoretical Biology 386:62–68. (2015)
- Discharge and manipulation of labial gland secretion by workers of Apis mellifera (L.)(Hymenoptera: Apidae). Proceedings of the Royal Entomological Society of London 39:76–82. (1964)
- Drag Reduction in the Mouthpart of a Honeybee Facilitated by Galea Ridges for Nectar-Dipping Strategy. Journal of Bionic Engineering 12:70–78. (2015)
- Drag reduction effects facilitated by microridges inside the mouthparts of honeybee workers and drones. Journal of theoretical biology 389:1–10. (2016)
- Nectar selection by melipona and Apis mellifera (Hymenoptera: Apidae) and the ecology of nectar intake by bee colonies in a tropical forest. Oecologia 61:1-10. (1984)
- Die sinnesorgane an der glossa, dem epipharynx und dem hypopharynx der arbeiterin von Apis mellifica L. (Insecta, Hymenoptera). Zeitschrift für Morphologie der Tiere 70:201–228. (1971)
- Electrophysiological responses of galeal contact chemoreceptors of Apis mellifera to selected sugars and electrolytes. Journal of insect physiology 22:1609–1616. (1976)
- Motor innervation and proprioceptors of the mouthparts in the worker honey bee, Apis mellifera. I. Mandibular nerve. Journal of Morphology 188:51–67. (1986)
- Motor innervation and proprioceptors of the mouthparts in the worker honey bee Apis mellifera. II. Maxillary and labial nerves. Journal of Morphology 201:23–37. (1989)
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